This invention relates to a versatile time difference comparison compensation method of a control system for control equipment and control systems, particularly for a servo mechanism, then for a continuous-data control system and for process control system and the like.
In order to accomplish any of the objects such as improvement in quickness of response, reduction of dispersibility, improvement in gain margin and/or phase margin, reduction of response to disturbance and restriction of a manipulation variable, compensation methods that have been employed conventionally in a feedback control system constituting control equipment and control system include, in the aspect of analog control, feedback control such as tachometer feedback, phase lag compensation, phase lead compensation, compensation by a PID controller (J. G. Ziegler and N. B. Nichols: "Optimum Settings for Automatic Controllers", Trans. ASME, Vol. 64, P759-768 (1942)) and a Smith's method (O. J. M Smith: "A Controller to Overcome Dead Time", ISA Journal, 6-2, P28-33 (1959)), and in the aspect of digital control, dead beat control, optimal control, adaptive control, and a compensation method by an utmost compensator (R. Tagawa: "On the compensation in linear feedback control systems (Transfer functions attainable by realizable linear compensation)", IFAC World Congress/'81, Kyoto (1981)). These many methods have mutually different characteristics and are applied suitably to a control system as the object of control.
In the case of analog control, however, further improvement cannot be expected any more by any of the methods described above in quickness of response, reduction of dispersibility and gain margin and/or phase margin. In digital control, on the other hand, a control system almost approximate to the ultimate system has now been established with expansion, development and preparation of its control theory, but it is essentially impossible to satisfy simultaneously all of the requirements ranging from the improvement in quickness of response, reduction of dispersibility, restriction of a manipulation variable, securing of stability, and so forth. Therefore, various digital control methods have been devised depending upon which of these requirements must be better satisfied or how the balance of these requirements is established. However, in any of these digital control methods, a large number of days and a great deal of labor have been necessary for the design and architecture of the system because the control system is complicated and arithmetic analysis is very difficult. Moreover, design and architecture must often be made once again from the beginning with only a limited change of a controlled system. Therefore, setting, adjustment and re-adjustment of a control apparatus containing each control method or each compensation method are generally difficult, and it is difficult to say that the control method or compensation method of digital control which takes into consideration the dead time attendant to many controlled systems and/or the delay by the processing time of a microprocessor into consideration has been established. It is also difficult to say that in both cases of analog control and digital control, each of the compensation methods or control methods in accordance with the prior art has sufficient versatility to various control equipment and control systems.